1. Field of the Invention
From the Sacramento Valley southward through California and throughout the southwest and in parts of the southern regions and plains states, natural rain fall has typically been inadequate to permit efficient reclamation and use of the indigenous arid soils for agricultural purposes. These lands were reclaimed and made productive through the development of elaborate, although somewhat rudimentary, irrigation systems.
Water sources vary, depending on location, and include storage reservoirs, canals, natural water courses and, of course, subterranean alluvial flow, which is retrieved by the use of expensive pumps.
The cost of water, of course, is dear and while years of research, much of which is at the university level, has taught the farmer "how much" water each crop should receive, given the parameters of soil conditions, evapotransportation rate and the type of crop itself, efficient delivery of water to the farmer's field in the proper amounts continues to be, in many parts of the country, an essentially manual task. Probably the most common approach is referred to as flood irrigation, most vividly conceptualized by the rice farmer. In such cases, the field to be irrigated is typically leveled so as to provide a modest decrease in elevation from the water source to the portion of the field most remote from the water source where the remaining water is collected and disposed of. The field is provided with small dikes and water from the source is permitted to flood the field and "soak in". The typical consequences which result from employing such a method is that a certain amount of runoff, or residual water hereinafter referred to as "tail water", is produced which must be disposed of by draining it away from the field. That water may be lost to the farmer, resulting in a certain amount of waste.
A more modern approach is the surge irrigation approach. Its proponents indicate that this method of irrigation possesses numerous advantages such as faster water distribution, increased uniformity in application, a reduction in the initial pumping costs, and a reduction in tail water losses, all of which are true, to a greater or lesser extent, depending upon the particular application.
2. Description of the Prior Art
The prior art is replete with numerous examples of assorted irrigation devices which have been designed for particular irrigation applications. Examples include drip and sprinkler irrigation techniques which are discussed in the reference to Pollock, U.S. Pat. No. 4,317,539 and in the reference to Bently, U.S. Pat. No. 3,974,853, both of which are employed most frequently with respect to certain trees and vines.
Whether a flood or surge method of irrigation is employed, the prevalent prior art practice of transporting water to the fields includes three major techniques. The first technique entails simply cutting a dike between a source of ditch water and the field so as to permit uncontrolled flow of the ditch water into the field.
The second technique employs syphon tubes which are disposed in fluid-flow relation between the source of ditch water and the field. Common to row crop applications, the syphon tube irrigation method is employed to draw water out of the ditch and into the fields without cutting the dike. As should be understood, this method requires that one or more individuals actually walk to the field, prime the syphon tubes, and then put them in position such that they are operable to draw water from the ditch and deliver it to the field. Thereafter, and once the requisite amount of water has been applied, these same individuals must come back and break the syphon and remove the syphon tubes to prevent further water flow.
The third technique utilizes conduits which are filled with water from a pressure source, such as a pump, or where water is delivered to a standpipe connected to the conduit. The standpipe, when used, is of a predetermined height which will support heads, which may range from two to thirty feet. The heads, of course, permit the water to be delivered through the conduit system to risers in the field. Each of the risers is equipped with a manually operated gate or like valve arrangement, which must be manually opened and closed. The overflow riser valve apparatus manufactured by Waterman Industries, Inc. is an example of such a device. In certain other row crop irrigation systems, lengths of gated pipe are mated in fluid-flow relation with larger valves, the device being adapted selectively to feed a predetermined number of furrows simultaneously.
While the prior art practices operate with varying degrees of success, they have numerous shortcomings which have detracted from their usefulness. The most obvious drawbacks to the various systems previously described include the inability of the previous methods adequately to control the volume of water applied, the inability to apply that water uniformly over the surface area of the field, the creation of an unacceptable amount of tail water and power usage, and a huge expenditure of labor with the coincident expense thereof.
The value of automating irrigation systems to some extent is recognized in the prior art. More particularly the reference to H. R. Haise et al., U.S. Pat. No. 3,320,750 discloses the use of inflatable bladders to restrict irrigation flow. Similarly, the reference to Mitchell, U.S. Pat. No. 1,873,138 recognizes the use of rubber bladders in a general purpose valve arrangement. As a general proposition, it has been recognized that automation of commercial irrigation systems provides certain significant benefits, and that the use of fluid pressure actuated valves in particular, has some utility. With the advent of computer automation, remotely operable subassemblies have taken on a new importance.
Notwithstanding the teachings heretofore discussed, neither the state of the prior art as practiced at the time of the present invention, nor other prior art efforts to devise suitable irrigation controls, either anticipate the means, nor achieve the same laudable results, capable of being achieved by use of the present invention.